Pull tab for cam lock sliders

ABSTRACT

A cam lock slider for slide fasteners and a method of making the same are disclosed, wherein there is provided a pull tab having cam means for locking the slider against movement on a slide fastener. The cam means comprises a pair of identical tongues bifurcated at one end of the body of the pull tab and each curled around a reinforcing core into the form of a roll, said reinforcing core being integrally formed with each tongue and held in intimate contact with the inner peripheral surface of the tongue when the latter is curled.

United States Patent Watanabe [451 July 29, 1975 PULL TAB FOR CAM LOCK SLIDERS [75] lnventor:

[73] Assignee: Y oshida Kogyo Kabushiki Kaisha,

Tokyo, Japan [22] Filed: July 25, 1974 [21] Appl. No.: 491,809

Related US. Application Data [62] Division of Ser. No. 426,666, Dec. 12, 1973.

Hirokazu Watanabe, Toyama, Japan [30] Foreign Application Priority Data Dec. 14, 1972 Japan 47-125428 [52] U.S. Cl. 29/409 [51] Int. Cl B2ld 53/54 [58] Field of Search 29/409, 400 D, 150, 408,

29/400 R, 207.5 SL; 24/205.l4

[56] References Cited UNITED STATES PATENTS 2,865,075 12/1958 Firing ..29/409X Primary Examiner-Thomas H. Eager Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT A cam lock slider for slide fasteners and a method of making the same are disclosed, wherein there is provided a pull tab having cam means for locking the slider against movement on a slide fastener. The cam means comprises a pair of identical tongues bifurcated at one end of the body of the pull tab and each curled around a reinforcing core into the form of a roll, said reinforcing core being integrally formed with each tongue and held in intimate contact with the inner peripheral surface of the tongue when the latter is curled.

1 Claim, 10 Drawing Figures PATENTEU JUL29 I975 FlG.4g

PATENTEU JUL 2 9 I975 SHEET FE 4c FiGJQ F1645 15a 27 21a 22a F FIGAd PULL TAB FOR CAM LOCK SLIDERS This is a division of application Ser. No. 426,666 filed Dec. 12, 1973.

BACKGROUND OF THE INVENTION This invention relates to improvements in cam lock sliders for slide fasteners, more particularly to the construction ofa slider pull tab, and to a method of making the same.

Generally, the pull tabs assembled on cam lock sliders are formed by die-casting or pressing a blank metal. While the die-casting process can advantageously produce locking cams of any adjusted shape and size, it has the drawback that restrictions are imposed upon the type of metals that can be die-cast and hence, the cam lock portions of a die-cast pull tab are relatively weak and susceptible to wear in repeated use. For this reason, most die-cast pull tabs are considered not suitable for sliders provided on mens trousers, labor uniforms and other garments or articles such that are handled' concentration of provided with locking cams of sufficient strength to withstand severe stresses and are mostly used on sliders attached to the above exemplified articles. A typical prior-art construction of such press-formed pull tab includes a cam or cams formed into a roll by bending over or curling a tongue at one end of the pull tab body. Such roll cam has resultant internal space and is therefore liable to become crushed or otherwise deformed when the garment is laundered or pressed.

A more recent cam lock slider is known wherein the pull tab is provided with a pair of identical cams formed from bifurcated tongues which are swaged inwardly from opposite sides so that a portion of the stock of each tongue is drifted downward to close up the space between the cams and the adjacent surface of the pull tab body. Such cams being solid may be exempt from becoming crushed as was encountered with the roll type of cam having an internal space. However, as a result of lateral swaging of the side wall of the tongue, the peripheral wall of the cam is thinned out or reduced for the amount of the stock being drifted to close up the aforesaid space. Therefore, such cam is not wholly satisfactory as regards mechanical strength. Another difficulty arising from such swaged cam is that the outer surface of its peripheral wall tends to incline inwardly relative to the plane of the pull tab so that when the pull tab is swung into locked position, the outer marginal edge of the cam wall alone abuts against the fastener elements and is therefore prone to become locally worn upon repeated locking operation of the slider. In addition, the method employed for the manufacture of such cams has the drawback that desired accuracy as regards the form and dimensions of the cam is difficult to achieve.

SUMMARY OF THE INVENTION Whereas, it is an object of the present invention to provide an improved cam lock slider of this character which will eliminate the above noted difficulties of the prior art sliders and which more specifically includes substantially solidly formed cams having sufficient thickness throughout their length to withstand greater pressure and desired accuracy as regards the form and dimensions such that their camming surfaces are disposed in uniformly effective locking engagement with the fastener elements.

This and other objects and features of the invention will be better understood from the following description taken in conjunction with the accompanying drawings which illustrates by way of example only a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS utilized to show different stages of forming the locking cams integrally with the pull tab.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in which like numerals refer to like parts throughout the several views, and firstly to FIG. 3, the numeral 10 refers generally to a slider having upper and lower spaced wing members 11 and 12 connected together at one end by an integral neck 13. The upper wing 11 is provided with a bail 14 to which a pull tab 15 is pivotally connected. The pull tab 15 is provided with a pair of identical, laterally spaced locking cam rolls 19,20 which are adapted to extend through respective slots 11a in the upper wing 11 when the pull tab is swung to locking position and press the fastener elements E against an internal recess 16 in the lower wing 12, thereby locking the slider against movement on a slide fastener (not shown).

The pull tab 15 which forms the subject matter of the present invention is shown in finished form in FIG. 1, and it comprises a rectangular body 17 provided at one end with an opening 18 for convenience in operating the pull tab and at the opposite end with a pair of locking cam rolls 19,20 formed by bifurcated tongues 21,22 extending on opposite sides of a slot 23 and bent over or curled backward each about a reinforcing core 24,

and opposed trunnions 25,26 extending inwardly from the inner edges of the tongues 21,22 into the slot 23 and adapted to connect the pull tab pivotally to the slider 10.

Referring to FIGS. 4a through 4g, there are shown different stages in the manufacture of the pull tab 15 according to the invention. In the first stage shown in FIG. 4a, a starting metal blank 15a is stamped out where indicated in hatched lines to form a square opening 18a at one end for convenience in manipulating the tab and to reveal scrap portion 27 contiguous to tongue-forming portions 21a, 22a at the opposite end. The chain-dotted lines indicate the contour along which the blank 15a is eventually cut or stamped out into a final form.

In the second stage of the operation, the scrap portions 27 are swaged from the position of FIG. 4b to the position of FIG. 4b" whereupon part of the stock of the scrap portions is drifted sidewise to provide a flattened ear portion 24a-which will be reformed subsequently into the reinforcing core 24. The scrap portions 27 are then cut away as shown in FIG. 40, leaving the flattened ears 24a with the tongue-forming portions 21a, 22a.

This cutting operation constitutes the third stage in which each ear 24a is provided with a rounded peripheral contour as shown, along which the tongue-forming portion 21a, (22a) is folded into a roll form as later described. In the fourth stage of the operation which is illustrated in FIG. 4d, the ear portions 24a are bent upright to project perpendicularly beyond the upper surface of the blank a, as this is seen from a change in the position from FIG. 4d to FIG. 4d".

In the fifth stage illustrated in FIG. 46, the blank 15a is stamped out where indicated in hatched lines to provide a polygonal opening or slot 2311, on opposite sides of which slot are formed bifurcated tongue-forming portions 21a, 22a. The slot 23a is configured such that there are produced inwardly extending opposed trunnions 25,26.

The bifurcated tongues 21,22 are bent over or curled progressively backward as depicted in FIG. 4f and better in FIG. 4] which constitutes the sixth stage wherein the ear portion 24a serves as a winding core 24 about which each tongue is bent. During this bending operation, the ear portion 24a is rotated in position and is brought into intimate contact with the inner peripheral surface 28 of each tongue adjacent the trunnion 25,(26) thereby filling the space which would otherwise be formed in the curled tongue. The ear portion 24a now thus functions as the reinforcing core 24 adapted to prevent the tongue 2l,(22) from being crushed.

The blank 15a is finally processed to remove by cutting the longitudinal marginal scrap portions 30 as shown in FIG. 4g. The pull tab 15 resulting from this final stage may be further processed to spread apart the bifurcated tongues 21,22 to the position shown in FIG. 1, if necessary, to facilitate the assembling of the pull tab to the bail 14 of the slider 10.

Advantageously, the locking cam rolls 19,20 formed by the bifurcated tongues 21,22, respectively, after the various stages of the press-forming operation can retain sufficient strength against severe external pressure because the thickness (t') of the tongue 2l,(22) as measured diametrically of the cam roll remains equal to the thickness (t) of the blank 15a, as shown in FIG. 2. Also advantageously, because the ear portions 24a which subsequently form the reinforcing cores 24 are swaged prior to the curling of the tongues 21,22 thereabout, the shape and dimensions of the resulting cam rolls 19,20 can be defined with reasonable accuracy by the peripheries of the swaged ear portions and can thus be held uniform throughout the product pull tabs. Further advantageously, the tongue 2l,(22) is bent over with its outer peripheral surface or camming surface 29 lying in a plane parallel with the plane of the upper surface of the pull tab body 17, so that the cam roll l9,(20) can abut uniformly through its entire camming surface against the fastener elements E to effect reliable locking of the slider upon the fastener elements.

Having thus described the invention, it will be understood that the invention is not to be limited to the precise form and construction herein advanced, but various changes or modifications may be made therein without departing from the scope of the appended claims.

What is claimed is:

1. A method of making a pull tab for slide fastener sliders which comprises the steps of:

a. swaging a tab forming blank adjacent one end to produce a pair of laterally extending ear portions of reduced thickness;

b. erecting said ear portions so as to project perpendicularly beyond the upper surface of said blank;

c. stamping out said blank to form a polygonal opening adjacent said one end and between said ear portions, resulting in bifurcated tongue portions extending on opposite sides of said opening and now having said ear portions at their respective outer edges, and in inwardly directed opposed trunnions by which the pull tab is connected pivotally to a slider; and

d. bending each of said tongues over backward around said erected ear portion substantially into the form of a roll serving as a cam roll, with said ear portion being held in intimate contact with the inner peripheral surfaces of said tongue. 

1. A method of making a pull tab for slide fastener sliders which comprises the steps of: a. swaging a tab forming blank adjacent one end to produce a pair of laterally extending ear portions of reduced thickness; b. erecting said ear portions so as to project perpendicularly beyond the upper surface of said blank; c. stamping out said blank to form a polygonal opening adjacent said one end and between said ear portions, resulting in bifurcated tongue portions extending on opposite sides of said opening and now having said ear portions at their respective outer edges, and in inwardly directed opposed trunnions by which the pull tab is connected pivotally to a slider; and d. bending each of said tongues over backward around said erected ear portion substantially into the form of a roll serving as a cam roll, with said ear portion being held in intimate contact with the iNner peripheral surfaces of said tongue. 